fused-effects-exceptions (empty) → 0.1.0.0

raw patch · 5 files changed

+146/−0 lines, 5 filesdep +basedep +fused-effectsdep +safe-exceptionssetup-changed

Dependencies added: base, fused-effects, safe-exceptions

Files

• LICENSE +30/−0
• README.md +5/−0
• Setup.hs +2/−0
• fused-effects-exceptions.cabal +28/−0
• src/Control/Effect/Catch.hs +81/−0

@@ -0,0 +1,30 @@+Copyright Josh Vera (c) 2019++All rights reserved.++Redistribution and use in source and binary forms, with or without+modification, are permitted provided that the following conditions are met:++    * Redistributions of source code must retain the above copyright+      notice, this list of conditions and the following disclaimer.++    * Redistributions in binary form must reproduce the above+      copyright notice, this list of conditions and the following+      disclaimer in the documentation and/or other materials provided+      with the distribution.++    * Neither the name of Patrick Thomson nor the names of other+      contributors may be used to endorse or promote products derived+      from this software without specific prior written permission.++THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

@@ -0,0 +1,5 @@+# fused-effects-exceptions++This package provides functionality to handle exceptions thrown in the `IO` monad. It delegates to `catch` from `Control.Exception`. An additional `catchSync` primitive is provided to handle the common case of catching only synchronous exceptions.++This implementation was extracted from one originally written by Josh Vera. It requires a version of `fused-effects` later than 0.3.

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,28 @@+name:                fused-effects-exceptions+version:             0.1.0.0+synopsis:            Handle exceptions thrown in IO with fused-effects.+description:         Provides an effect that enables catching exceptions thrown from impure computations such as 'IO'.+homepage:            https://github.com/patrickt/fused-effects-exceptions#readme+license:             BSD3+license-file:        LICENSE+author:              Josh Vera+maintainer:          patrickt@github.com+copyright:           2019 Josh Vera and Patrick Thomson+category:            Control.+build-type:          Simple+cabal-version:       >=1.10+extra-source-files:  README.md++tested-with:         GHC == 8.6.4++library+  hs-source-dirs:      src+  default-language:    Haskell2010+  exposed-modules:     Control.Effect.Catch+  build-depends:       base >= 4.7 && < 5+                     , fused-effects >= 0.3 && <1+                     , safe-exceptions >= 0.1 && <1++source-repository head+  type:     git+  location: https://github.com/fused-effects/fused-effects-exceptions

@@ -0,0 +1,81 @@+{-# LANGUAGE DeriveFunctor, ExistentialQuantification, FlexibleContexts, FlexibleInstances, GeneralizedNewtypeDeriving,+             MultiParamTypeClasses, RankNTypes, StandaloneDeriving, TypeOperators, UndecidableInstances #-}++-- | An effect that enables catching exceptions thrown from+-- impure computations such as 'IO'.+--+-- Use of the 'Control.Effect.Error' effect from @Control.Effect.Error@ may lead to+-- simpler code, as well as avoiding the dynamically-typed nature of+-- 'Control.Exception'. This is best used when integrating with third-party+-- libraries that operate in 'IO'. If you are using 'catch' for resource+-- management, consider using 'Control.Effect.Resource' instead.+module Control.Effect.Catch+  ( Catch (..)+  , catch+  , catchSync+  , runCatch+  , CatchC (..)+  ) where++import           Control.Effect.Carrier+import           Control.Effect.Reader+import           Control.Effect.Sum+import qualified Control.Exception as Exc+import           Control.Exception.Safe (isSyncException)+import           Control.Monad.IO.Class++data Catch m k+  = forall output e . Exc.Exception e => CatchIO (m output) (e -> m output) (output -> k)++deriving instance Functor (Catch m)++instance HFunctor Catch where+  hmap f (CatchIO go cleanup k) = CatchIO (f go) (f . cleanup) k++instance Effect Catch where+  handle state handler (CatchIO go cleanup k)+    = CatchIO (handler (go <$ state)) (\se -> handler (cleanup se <$ state)) (handler . fmap k)++-- | Like 'Control.Effect.Error.catchError', but delegating to+-- 'Control.Exception.catch' under the hood, which allows catching+-- errors that might occur when lifting 'IO' computations.+-- Unhandled errors are rethrown. Use 'Exc.SomeException' if you want+-- to catch all errors.+catch :: (Member Catch sig, Carrier sig m, Exc.Exception e)+      => m a+      -> (e -> m a)+      -> m a+catch go cleanup = send (CatchIO go cleanup pure)++-- | Like 'catch', but the handler only engages on synchronous exceptions.+-- Async exceptions are rethrown.+catchSync :: (Member Catch sig, Carrier sig m, Exc.Exception e, MonadIO m)+          => m a+          -> (e -> m a)+          -> m a+catchSync f g = f `catch` \e ->+  if isSyncException e+      then g e+      -- intentionally rethrowing an async exception synchronously,+      -- since we want to preserve async behavior+      else liftIO (Exc.throw e)++-- | Evaulate a 'Catch' effect.+runCatch :: (forall x . m x -> IO x)+         -> CatchC m a+         -> m a+runCatch handler = runReader (Handler handler) . runCatchC++newtype Handler m = Handler (forall x . m x -> IO x)++runHandler :: Handler m -> CatchC m a -> IO a+runHandler h@(Handler handler) = handler . runReader h . runCatchC++newtype CatchC m a = CatchC { runCatchC :: ReaderC (Handler m) m a }+  deriving (Functor, Applicative, Monad, MonadIO)++instance (Carrier sig m, MonadIO m) => Carrier (Catch :+: sig) (CatchC m) where+  eff (L (CatchIO act cleanup k)) = do+    handler <- CatchC ask+    liftIO (Exc.catch (runHandler handler act) (runHandler handler . cleanup)) >>= k+  eff (R other) = CatchC (eff (R (handleCoercible other)))